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Abstract

Various clay stabilizers are discussed and methods are proposed for evaluating their effectiveness. Laboratory tests are proposed for evaluating their effectiveness. Laboratory tests are used to rate the relative efficiency of potassium chloride vs other salts and organic compounds. Advantages and limitations of the various clay stabilizers are described. These studies show that increased temperature improves the efficiency of KCl and that pH is not significant factor, except in low-salinity solutions. Alternate materials are sometimes superior to KCl, but care must be taken when using substitute products.

Introduction

The control of clay swelling and migration is an important consideration in the design of any stimulation treatment. The response of water-sensitive formations to contact with stimulation fluids can exert a major influence upon ultimate well productivity. It is important to carefully evaluate formation productivity. It is important to carefully evaluate formation sensitivity and select the most compatible completion and stimulation fluids.

Clay stabilizers are routinely added to aqueous stimulation and completion fluids to prevent damage to the formation. These clay stabilizers can be of either a temporary or permanent type, and are often used in combination. Temporary or permanent type, and are often used in combination. Temporary or permanent type, and are often used in combination. Temporary permanent type, and are often used in combination. Temporary clay stabilizers are materials such as KCl, NH4Cl, CaCl2 and NaCl which, when added to fresh water, prevent the injected fluid from swelling or dispersing clays. While these products prevent aqueous treating fluids from damaging the formation prevent aqueous treating fluids from damaging the formation they provide no long-term protection.

Permanent clay stabilizers, such as zirconium salts, hydroxy-aluminum and certain polycationic polymers, irreversibly attach to cation exchange sites on the clays and are not displaced by other cations present in formation water. These materials permanently stabilize sensitive clays. The permanent clay stabilizers are usually applied using a carrier permanent clay stabilizers are usually applied using a carrier fluid containing a temporary stabilizer, such as KCl, to prevent the carrier fluid itself from damaging the formation.

Of the temporary clay stabilizers, KCl is the product most commonly used. It is quite effective and is routinely added to aqueous fracturing fluids at concentrations of 1% to 3%. Other salts, such as NaCl, NH4Cl and CaCl2, have also been proposed for this application. proposed for this application. P. 7-1 P. 7-1

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